Bendable plywood sheets are known for use in furniture construction, as well as in architectural applications where a curved or rounded wooden surface is desired. Conventional bendable plywood is a 3-ply construction using a thin high density hardwood inner core ply with two thick low density outer plies of fast growth rotary cut veneer.
FIG. 1 shows a conventional bendable plywood panel 10 which typically is manufactured and sold in standard size rectangular sheets having a 1.25 meters (4 feet) length of grain and a width of 2.5 meters (8 feet) across the grain. The panel 10 is constructed so as to enable it to be bent in a bending direction BD parallel to its longitudinal elongated length, without requiring the pre-application of heat or moisture, and without producing a significant degree of checking, cracking or splintering in the face ply panel layer.
To provide the panel 10 with its bending properties, FIG. 2 shows best the panel 10 as having a three-ply construction. The panel includes outer ply or layers 12,14 of 4.25 mm thick fuma veneers which are adhesively bonded to respective sides of a 0.7 mm thick birch or hardwood core veneer 16 by layers of an adhesive 18a,18b. As shown best in FIG. 1, to enable bending of the panel 10 in the bending direction BD, each of the veneer layers 12 and 14 is formed from a low density wood rotary-cut veneer, with the core ply 16 being comparably thin. The veneers 12,14 and 16 are then laminated together with the grain directions GD of the layers 12,14 elongated in the same direction, and oriented parallel to the lateral width of the panel 10 and at right angles of that of the layer 12.
A disadvantage exists with conventional bendable plywood panels 10 in that to prevent cracking of the veneer layers 12,14 heretofore such panels have been formed with a thickness of less than about 0.9 cm. It has been found that where thicker plywood panels have been provided, the veneer layers 12,14 are susceptible to cracking, checking or splintering. As a result, where thicker plywood panels are desired, heretofore it has been necessary to individually bend, position and adhere together multiple panels, increasing both product manufacturing difficulties, and expense.
Conventional prior art bendable plywood panels suffer a further disadvantage in that the use of rotary-cut veneer layers 12,14 as the outer facing surfaces of the panel 10 typically provide an aesthetically displeasing appearance. In particular, rotary-cut veneer layers often present a roughened or deeply pitted wood grain, making the veneer layers 12,14 of the panel 10 unsuitable for direct finishing by staining or painting. As a result, architects or furniture manufacturers typically will finish the article or architectural component by subsequently applying a further hardwood veneer layer, such as cherry, oak or the like to the surface of the bent plywood once it has been preformed. As a result, following initial fabrication of the furniture or architectural component, it is thereafter necessary to then apply to the panel 10 a select or finished grade veneer such as an oak or cherry veneer over one or both of the bent fuma veneers 12,14, to achieve the desired look. In addition to increasing manufacturing time, the necessity of separately applying finishing veneers increases the chance of workmanship defects, as well as production costs.